This article takes an in depth look at conveyor ovens.
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A conveyor oven is a continuous flow oven; it‘s an oven that is open on opposing sides and has a conveying system running from one end of the oven to the other. Designed like a batch oven, conveyor ovens have the additional benefit of keeping products moving while providing continuous and uniform heat. They are ideal for mass production and massive product runs.
There are various types of conveying systems available for conveyor ovens; this includes overhead, chain on edge, roller, belt, and chains of differing sizes, shapes, and types. Products to be processed can be a few pounds or several hundred pounds.
Industrial ovens are a heated chamber that are a vital part of manufacturing and finishing processes. They provide an enclosure for heat treating parts and components that require curing, annealing, or other forms of high temperature treatments. Conveyor ovens are a type of industrial oven that continuously, steadily, and reliably move parts through an oven chamber for heat treatment and processing.
Conveyor industrial ovens are custom designed to treat a specific type of material and use a variety of conveying methods and types of heating elements. A critical aspect of conveyor ovens is the air flow, which can be horizontal/vertical or vertical/horizontal depending on the oven‘s design.
Vertical conveyor ovens, paternoster type, are used where there is limited floor space. Parts are conveyed using vertically moving trays that can be indexed or continuously moving. The trays are fixed on conveyor chains that move according to the paternoster pattern. Vertical conveyor ovens have exceptional temperature uniformity, reliable mechanics, low maintenance, and easy access.
Overhead conveyor ovens use an overhead conveying system similar to a monorail to move parts to be treated by multiple processes. They are an ideal solution for processing high volumes of components and parts. An overhead conveyor oven has a continuous circuit chain running on a through track with vertical and horizontal curves that connect to a drive unit that pulls the chain.
Belt conveyor ovens have a woven chain belt that moves parts and materials through the oven. The belt can be designed to move continuously or index and dwell depending on production volume and timing. Belt conveyor ovens are ideal for processing huge volumes of small parts and are a safe, reliable solution to part heat treatment. Parts are placed on the wire mesh belt and slide on a steel slider bed.
Chain-on-edge or spindle conveyor systems have a chain mounted on the floor or a frame with posts attached to the chain that have some form of fixture. Parts are loaded onto the spindles or posts to be conveyed through the oven, and they can be configured for multiple oven passes. As with the other types of conveyor ovens, the chain-on-edge version can be programmed for continuous flow or indexing. Much like the belt version, chain-on-edge conveyor ovens are a perfect solution for small high volume parts.
Tunnel ovens are typically used to process food and are designed with high temperature capabilities. As with all conveyor ovens, tunnel ovens come with a variety of heat sources, from infrared to direct gas fire, and use any of the different types of conveying systems. Tunnel ovens can have multiple heat and cooling zones with adjustable conveying speeds and can be integrated into an existing conveying system.
Infrared heating is accomplished by electrical energy being generated in infrared wavelengths emitted from the surface of the heating element. The heat waves travel continuously until they make contact with an object. With an infrared conveyor oven, infrared heating is an efficient and homogeneous method for heating products. Infrared conveyor ovens can have controllable and programmable heat zones that offer thermal control of the heating process.
The key factor for an electric convection conveyor oven is the continuous circulation of the heated air by a fan or other source. The circulating mechanism pulls air from one section of the oven and pushes it back into the oven. The process maintains uniform temperature throughout the heated space and brings more heated air into contact with the elements being treated.
Gas heated conveyor ovens have burners above and below the conveying mechanism. For improved uniform heating, a gas and air mixture are supplied to the burners, which are ignited by a spark electrode. Heat is transferred from the gas flames, the oven top, base, and walls by radiation. The burners operate on zero gas pressure with air supplied by blowers. The belt is made of woven wire mesh or heavy meshed steel.
Carousel conveyor ovens allow for the loading and unloading of the treated product in the same location. This method of conveying offers the flexibility of varying quantities to be loaded, what sizes can be loaded, and the facilitation of personnel. Carousel conveyor ovens use horizontal airflow and save floor space.
A common design practice for conveyor ovens is to combine various heating methods. The combinations include gas and indirect radiant, gas and convection, and ovens using three heating systems such as gas, radiant, and convection. The benefits of combining heat sources is an optimization of energy consumption and faster processing times.
All conveyor ovens are specially designed and engineered to meet the needs of the customer. When planning the purchase of a conveyor oven, there is a wide variety of factors that need to be considered, such as the material to be treated, oven configuration, how the oven will fit into the manufacturing process, and the type of belt material.
Conveyor oven belts can be made from several materials; these include fabric and metals. The determination of the belt material hinges on the oven's purpose—sintering, drying, annealing, or curing to name a few.
Carbon steel belts are durable, have precision tracking, and exceptional straightness and flatness. They are easy to clean, hygienic, and abrasion resistant. Carbon steel belts are commonly used in baking and food preparation. The down side of carbon steel is that it rusts and discolors.
Stainless steel is one of the most resilient metals used for industrial applications. It is the first choice for conveyor belts since it does not rust or corrode and does not require frequent cleaning. The strength, durability, and toughness of stainless steel makes it the ideal material for conveyor belts for several industries including rubber, lamination, wood, and chemicals.
The choice of rubber may seem to be unusual for a conveyor belt for a conveyor oven since it easily melts . For rubber to be used for a conveyor oven, it is specially treated to be able to withstand temperatures of 450° F (232° C). Once treated, rubber is the perfect choice for food preparation conveyor ovens.
Of the many available choices for conveyor oven conveyor belts, plastic would seem to be the least likely. Plastic cannot be used in high temperature applications but is ideal for cooling chambers and low heat processes. It is cost effective, has a long usage life, and requires little maintenance. Plastic conveyor belts are made in linked sections, which makes them easier to remove and replace.
Polypropylene is adaptable for several applications and has the advantages of all plastic belts, and it is lightweight, sturdy, and flexible. It is resistant to water, mold, abrasion, chemicals, and corrosion. Of the various materials, polypropylene is the most versatile.
When fabric is being used as a conveyor belt for a conveyor oven, it is coated in TeflonTM, which makes the fabric non-stick and heat resistant. This type of conveyor belt is used in industrial ovens for baking and drying applications in food production in order to be in compliance with Federal Food and Drug Administration (FDA) rules.
Chain conveyor belts have two or more strands of chain designed to support a flat product in the shape of a board; this is placed on top of the chain strands. An alternative to the simple chain design is securing steel slats between the strands, a formation that allows smaller parts to be processed.
In an overhead conveying system, each link of the conveyor belt system is attached to another link to form a loop. Overhead chain systems allow for turns and elevation changes. The chain is connected to a motor that pulls it and is hung from a trolley or rail.
Flat wire conveyor oven belts are the most common and widely used. This type of oven belt is a piece of flat wire bent into a series of interlocked pickets that are connected by pins that run the width of the belt. Flat wire conveyor belts are made from wire of different thicknesses depending on the strength required for the application.
Balanced weave conveyor belts have the appearance of woven cloth but with threads made of wire. They come in different mesh and wire gauge types and styles. The width of the weave is wide enough to let air flow through but small enough to prevent small parts from falling through the mesh.
Roller conveyors are used for heavy loading applications and have flexibility of motion. Their use depends on the processing temperature.They have shaft bearings on the outside of the oven. The power transmission unit includes bearings, a system of chains, and a motor.
A walking beam conveying system is used when distance between materials is required. The pieces being moved through the oven are indexed using a static support and a moving support. The static support holds the material in place while the moving support moves it from one static support to the next. The process of lifting, moving, and holding takes place over the full length of the conveying system.
Walking beams are specially chosen for conditions where the environment prevents the use of the other conveying methods. Critical to the walking beam process are drive components and positioning sensors.
Every industry that deals with finishes, coatings, annealing, or other heat treatment processes uses a conveyor oven as an efficient and economical processing method. Many industrial operations necessitate the use of a conveyor oven due to the volume of products they produce that require heat treatment.
From drying to curing, conveyor ovens are capable of quickly completing processing continuously and easily. They can be adapted to an assembly process and engineered to fit smoothly into an existing conveying system.
The purpose of a conveyor oven in a drying process is to remove moisture or other liquids from a product. In most cases, multiple heat zones are necessary for maximum drying efficiency. For safety purposes, an exhaust system is built into the conveyor oven to match the moisture release rate.
The curing process raises the mass and coated material of a product to the appropriate temperature, holds it, and lets the product cool. The process is used to cure powdered coatings, paints, and adhesives. When a part is cured, the coating is hardened and toughened by the initiation of chemical structural changes in the coated material.
Heat treatment for aging involves elevating the temperature of a product to change its properties; this is also referred to as precipitation hardening to increase the hardness of a material. The process involves heating the material and keeping it at the raised temperature for hours, an ideal process for a conveyor oven.
Annealing is a heat treatment process that is typically performed on hard metals to change their microstructure for shaping and deforming. It increases ductility and eliminates internal stress. Annealing must be performed under precisely controlled conditions, so the microstructure is not damaged or severely altered.
Stress relieving is another metal changing method where the metal is heated to below its critical temperature then cooled. The heated temperature is held long enough to achieve the desired stress reduction. Since conveyor ovens do not apply flame to heat materials, they are an ideal method for relieving metal stress.
Bonding is a manufacturing heating process used to join multiple materials to create one material. The bonding process enhances the strength of the bonded materials with seams that are tighter and stronger than the original materials.
Tempering reduces the hardness of a metal; it is applied to ferrous alloys, such as steel and cast iron. When the hardness of the metal is decreased, the metal achieves greater toughness. As the hardness is reduced, the metal becomes more ductile and less brittle.
Conveyor ovens for food preparation are associated with cooking pizza, hot sandwiches, and donuts. The benefit of a conveyor oven for mass cooking is the steady heat it provides and how quickly it cooks. In food production, conveyor ovens significantly increase production and are able to bake or cook products in high volume.
Most manufacturing processes that require the use of a heat treatment process have their conveyor ovens specially designed to fit their method of production. Industrial operations demand the ovens they use be custom made to fit their product and be process specific.
Companies looking to purchase and install a conveyor oven compile information for the oven producer, so the final product matches the needs of the operation. Though each manufacturer has a different set of criteria, there are some generic factors to consider when planning a conveyor oven system.
The two basic types of conveying ovens are continuous and indexed; continuous ovens move treated products through at a constant rate and are designed for high volume operations. Indexing systems are stop and go systems; they use incremental motions to automate heating and cooling sequences.
The heat source can be the most expensive part, and its use may require adjustments to the manufacturing facility. Conveyor ovens are designed to be heated by electricity, natural gas, petroleum gas, or radiant heat. Hybrid models use multiple heating methods and can be economical. Electrical heat supplies depend on the operating voltage of the location with some units having dual voltages of 120 and 240.
The required temperature is dependent on the needs of the product and what is needed from the heating process. The minimum and maximum temperatures must be ascertained and are crucial to the conveyor oven buying decision. The design of conveyor ovens allows them to vary the heat treatment being applied to the material in various zones. Programmable logic controllers (PLC) give operators the option to control the effects of heat in zones of the oven.
The thermal process or profile is a description of how quickly the product needs to be heated, the length of the heating process, and whether it will need to be cooled and reheated. This aspect of the process is a reconsideration of the factor of temperature.
The heating phase determines the amount of heat required, while the cooling phase emphasizes the safe temperature to which the item can be cooled without harming it. A constant and central consideration when making the decision to purchase a conveyor oven is all aspects and parameters of temperature, which is the main reason for implementing a conveyor oven.
In any heating operation, air flow is a critical factor. A well-engineered and designed conveyor oven meticulously plans the air flow patterns to facilitate a faster time to temperature ratio to transfer heat efficiently and ensure oven heating uniformity. Air flow patterns can be top to bottom or bottom to top or a combination.
Proper air flow design enhances the performance of the conveyor oven and makes its operation safer.
There are a countless number of conveying systems that include traditional belt configurations made of various materials as well as monorail and tray designs. The determining factor for the type of conveying system is highly dependent on the product to be treated and its size, weight, material, and portability. Though most conveyor ovens have the traditional rectangular formation open at opposing ends, this type does not work for all manufacturing processes.
Among conveying system choices are the types of materials to be used to make the system; these can be various forms of wire mesh, rubber, and Teflon coated fabric.
One of the easiest aspects of selecting a conveying oven system is the space where it will be located. Every conveyor oven manufacturer has an oven that can fit into any location regardless of size. The different types include vertical systems that have a very small footprint and horizontal systems that come in several sizes, from those that will fill a building to those that can fit in the corner.
Managers and planners for all industries calculate the space they have for additional equipment and materials. It is one of the basic steps of the process. In the case of a conveyor oven, the more robust the oven, the more space it will require.
The purpose of purchase, implementation, and installation of a conveyor oven is quality and performance enhancement of a product. The specifications for the product and its treatment requirements are the guiding principles when selecting a conveyor oven. The factors to be considered when choosing a conveyor oven for the job include the product‘s degree of flammability, shape, dimensions, orientation, weight, and how the product will be heat treated, such as individually or in batches.
Modern manufacturing has a wide and varied number of control methods, each of which is customized to fit the type of conveyor oven they produce. Producers have developed PLC systems that can precisely control every function of a conveyor oven. The more automated a manufacturing process, the greater the need for technical control systems.
When it comes to heat treatment processes for manufacturing, there is a wide assortment of methods. In essence, a conveyor oven is a batch oven with the items to be treated in motion using horizontal, vertical, inclined, or spiral paths.
While batch ovens leave the product in a static position during thermal processing, conveyor ovens offer the flexibility of heat treating the product, positioning it for further processing, or completing multiple functions as the product moves through the system. These multiple operations make conveyor ovens a better choice for automating a manufacturing operation.
A conveyor oven system is a far superior choice for companies that have a high volume of products that need to be heat treated. With a static treatment system, products to be treated have to be loaded and unloaded from the oven. With a conveyor oven, products can be automatically loaded and unloaded, saving time and labor. Sometimes, the sheer volume of product handling operations necessitates the use of a conveyor oven.
Any production operation that moves products through its system with robotic and automated processes can use a conveyor oven; they will smoothly fit into any conveying and automated system. By installing a conveyor oven, the quality of products will be more consistent and uniform and production standards will be met.
Conveyor ovens are equipped with programmable logic controllers (PLC) that give operators the flexibility to change many of the factors related to the oven‘s operation. Residence time of a product in a heat zone can be adjusted as well as oven temperature, speed, air flow, and feed time.
Conveyor ovens are divided into zones, each of which can be changed and adjusted to match any variations in the product treatment process.
Unlike any other form of heat treatment method, conveyor ovens provide a consistent and uniform temperature to the heat treatment process. The product is perfectly timed and regulated as it passes through each zone.
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